< draft-pthubert-raw-problem-statement-00.txt		draft-pthubert-raw-problem-statement-01.txt >
	RAW P. Thubert, Ed.		RAW P. Thubert, Ed.
	Internet-Draft Cisco Systems		Internet-Draft Cisco Systems
	Intended status: Informational September 16, 2019		Intended status: Informational September 23, 2019
	Expires: March 19, 2020		Expires: March 26, 2020
	Reliable and Available Wireless Problem Statement		Reliable and Available Wireless Problem Statement
	draft-pthubert-raw-problem-statement-00		draft-pthubert-raw-problem-statement-01
	Abstract		Abstract
	This document describes the problem space for Reliable and Available		Due to uncontrolled interferences, including the self-induced
	Wireless at the IETF.		multipath fading, deterministic networking can only be approached on
			wireless links. The radio conditions may change -way- faster than a
			centralized routing can adapt and reprogram, in particular when the
			controller is distant and connectivity is slow and limited. RAW
			separates the routing time scale at which a complex path is
			recomputed from the forwarding time scale at which the forwarding
			decision is taken for an individual packet. RAW operates at the
			forwarded time scale. The RAW problem is to decide, within the
			redundant solutions that are proposed by the routing, which will be
			used for each individual packet to provide a DetNet service while
			minimizing the waste of resources.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on March 19, 2020.		This Internet-Draft will expire on March 26, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 19 ¶		skipping to change at page 2, line 26 ¶
	3. Routing Scale vs. Forwarding Scale . . . . . . . . . . . . . 4		3. Routing Scale vs. Forwarding Scale . . . . . . . . . . . . . 4
	4. Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . 5		4. Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . 5
	5. Functional Gaps . . . . . . . . . . . . . . . . . . . . . . . 5		5. Functional Gaps . . . . . . . . . . . . . . . . . . . . . . . 5
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
	6.1. Normative References . . . . . . . . . . . . . . . . . . 6		6.1. Normative References . . . . . . . . . . . . . . . . . . 6
	6.2. Informative References . . . . . . . . . . . . . . . . . 7		6.2. Informative References . . . . . . . . . . . . . . . . . 7
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	IP networks become more predictable when the effects of statistical		Bringing determinism in a packet network means eliminating the
	multiplexing (jitter and collision loss) are eliminated. This		statistical effects of multiplexing that result in probabilistic
	requires a tight control of the physical resources to maintain the		jitter and loss. This can be approached with a tight control of the
	amount of traffic within the physical capabilities of the underlying		physical resources to maintain the amount of traffic within a
	technology, e.g., by the use of time-shared resources (bandwidth and		budgetted volume of data per unit of time that fits the physical
	buffers) per circuit, and/or by shaping and/or scheduling the packets		capabilities of the underlying technology, and the use of time-shared
	at every hop.		resources (bandwidth and buffers) per circuit, and/or by shaping and/
			or scheduling the packets at every hop.
			Wireless networks operate on a shared medium where uncontrolled
			interference, including the self-induced multipath fading, adds
			another dimension to the statistical effects that affect the
			delivery. Scheduling transmissions can alleviate those effects by
			leveraging diversity in the spatial, time, code, and frequency
			domains, and provide a Reliable and Available service while
			preserving energy and optimizing the use of the shared spectrum.
	Deterministic Networking is an attempt to mostly eliminate packet		Deterministic Networking is an attempt to mostly eliminate packet
	loss for a committed bandwidth with a guaranteed worst-case end-to-		loss for a committed bandwidth with a guaranteed worst-case end-to-
	end latency, even when co-existing with best-effort traffic in a		end latency, even when co-existing with best-effort traffic in a
	shared network. It is getting traction in various industries		shared network. This innovation is enabled by recent developments in
	including manufacturing, online gaming, professional A/V, cellular		technologies including IEEE 802.1 TSN (for Ethernet LANs) and IETF
	radio and others, making possible many cost and performance		DetNet (for wired IP networks). It is getting traction in various
			industries including manufacturing, online gaming, professional A/V,
			cellular radio and others, making possible many cost and performance
	optimizations.		optimizations.
	This innovation is enabled by recent developments in technologies		Reliable and Available Wireless (RAW) networking services extend
	including IEEE 802.1 TSN (for Ethernet LANs) and IETF DetNet (for		DetNet to approach end-to-end deterministic performances in a network
	wired IP networks). Reliable and Available Wireless (RAW) networking		with scheduled wireless segments, possibly combined with wired
	services extend DetNet services to approach end-to-end deterministic		segments, and possibly sharing physical resources with non-
	performances in a network with scheduled wireless segments, possibly		deterministic traffic. The wireless and wired media are
	combined with wired segments, and possibly sharing physical resources		fundamentally different at the physical level, and while the generic
	with non-deterministic traffic.		Problem Statement for DetNet applies to the wired as well as the
			wireless medium, the methods to achieve RAW will differ from those
	Wireless networks operate on a shared medium, and thus transmissions		used to support time-sensitive networking over wires, as a RAW
	cannot be fully deterministic due to uncontrolled interferences,		solution will need to address less consistent transmissions, energy
	including the self-induced multipath fading. However, scheduling of		conservation and shared spectrum efficiency.
	transmissions can alleviate those effects by leveraging diversity in
	the spatial, time and frequency domains, providing a more predictable
	and available service.
	The wireless and wired media are fundamentally different at the
	physical level, and while the generic Problem Statement for DetNet
	applies to the wired as well as the wireless medium, the methods to
	achieve RAW will differ from those used to support time-sensitive
	networking over wires, and a RAW solution will need to address less
	consistent transmissions, energy conservation and shared spectrum
	efficiency.
	The development of RAW technologies has been lagging behind		The development of RAW technologies has been lagging behind
	deterministic efforts for wired systems both at the IEEE and the		deterministic efforts for wired systems both at the IEEE and the
	IETF. But recent efforts at the IEEE and 3GPP indicate that wireless		IETF. But recent efforts at the IEEE and 3GPP indicate that wireless
	is finally catching up at the lower layer and that it is now possible		is finally catching up at the lower layer and that it is now possible
	for the IETF to extend DetNet for wireless segments that are capable		for the IETF to extend DetNet for wireless segments that are capable
	of scheduled wireless transmissions.		of scheduled wireless transmissions.
	The establishment of the path is out of scope, and may inherit from a		The intent for RAW is to provide DetNet elements that are specialized
	centralized Architecture as described for DetNet and 6TiSCH, with a		for short range radios. From this inheritance, RAW stays agnostic to
	primary focus on scheduled wireless operations. As opposed to wire,		the radio layer underneath though the capability to schedule
	the action of setting up a path on a wireless network may be slow		transmissions is assumed. How the PHY is programmed to do so, and
	compared to the speed at which the transmission conditions vary, and		whether the radio is single-hop or meshed, are unknown at the IP
	the extra medium used for redundancy may be expensive. So in		layer and not part of the RAW abstraction.
	wireless, it makes sense for a centralized router to provide multiple
	forwarding solutions and leave it to the data plane to select which
	of those solutions are used fir a given packet based on the current
	conditions.
	The scope of the RAW WG will be protocol elements such as OAM to
	improve the forwarding decision along a path where intermediate nodes
	are capable of transmission redundancy, e.g., using packet
	replication and elimination, Hybrid ARQ and coding, but is
	constrained so as not to overuse this methods, eg., because energy
	and spectrum are limited.
	RAW should stay abstract to the radio layer (keep a layered
	approach). How the PHY is programmed, and whether the radio is
	single-hop or meshed, are unknown at the IP layer and not part of the
	RAW abstraction.
	Still, in order to focus on real-worlds issues and assert the		Still, in order to focus on real-worlds issues and assert the
	feasibility of the proposed capabilities, RAW will focus on selected		feasibility of the proposed capabilities, RAW will focus on selected
	technologies that can be scheduled at the lower layers: IEEE Std.		technologies that can be scheduled at the lower layers: IEEE Std.
	802.15.4 timeslotted channel hopping (TSCH), 3GPP 5G ultra-reliable		802.15.4 timeslotted channel hopping (TSCH), 3GPP 5G ultra-reliable
	low latency communications (URLLC), IEEE 802.11ax/be where 802.11be		low latency communications (URLLC), IEEE 802.11ax/be where 802.11be
	is extreme high throughput (EHT), and L-band Digital Aeronautical		is extreme high throughput (EHT), and L-band Digital Aeronautical
	Communications System (LDACS). See [I-D.thubert-raw-technologies]		Communications System (LDACS). See [I-D.thubert-raw-technologies]
	for more.		for more.
	RAW distinguishes the time scale at which routes are computed that we		The establishment of a path is not in-scope for RAW. It may be the
	qualify as slow from the forwarding time scale where per-packet		product of a centralized Controller Plane as described for DetNet.
	decisions are made. RAW operates at the forwarding time scale on one		As opposed to wired networks, the action of installing a path over a
	DetNet flow over one Track that is preestablished and installed by		set of wireless links may be very slow relative to the speed at which
	means outside of the scope of RAW. This is discussed in more details		the radio conditions vary, and it makes sense in the wireless case to
	in Section 3 and the next sections.		provide redundant forwarding solutions along a complex path and to
			leave it to the RAW Network Plane to select which of those forwarding
			solutions are to be used for a given packet based on the current
			conditions.
			RAW distinguishes the longer time scale at which routes are computed
			from the the shorter forwarding time scale where per-packet decisions
			are made. RAW operates at the forwarding time scale on one DetNet
			flow over one path that is preestablished and installed by means
			outside of the scope of RAW. The scope of the RAW WG comprises
			Network plane protocol elements such as OAM and in-band control to
			improve the RAW operation at the Service and at the forwarding sub-
			layers, e.g., controlling whether to use packet replication, Hybrid
			ARQ and coding, with a constraint to limit the use of redundancy when
			it is really needed, e.g., when a spike of loss is observed. This is
			discussed in more details in Section 3 and the next sections.
	2. Use Cases and Requirements Served		2. Use Cases and Requirements Served
	[RFC8578] presents a number of wireless use cases including Wireless		[RFC8578] presents a number of wireless use cases including Wireless
	for Industrial Applications. [I-D.bernardos-raw-use-cases] adds a		for Industrial Applications. [I-D.bernardos-raw-use-cases] adds a
	number of use cases that demonstrate the need for RAW capabilities in		number of use cases that demonstrate the need for RAW capabilities in
	Pro-Audio, gaming and robotics.		Pro-Audio, gaming and robotics.
	3. Routing Scale vs. Forwarding Scale		3. Routing Scale vs. Forwarding Scale
	skipping to change at page 5, line 49 ¶		skipping to change at page 6, line 6 ¶
	5. Functional Gaps		5. Functional Gaps
	Within a large routed topology, the routing operation builds a		Within a large routed topology, the routing operation builds a
	particular complex Track with one source and one or more		particular complex Track with one source and one or more
	destinations; within the Track, packets may follows different paths		destinations; within the Track, packets may follows different paths
	and may be subject to RAW forwarding operations that include		and may be subject to RAW forwarding operations that include
	replication, elimination, retries, overhearing and reordering.		replication, elimination, retries, overhearing and reordering.
	The RAW forwarding decisions include the selection of points of		The RAW forwarding decisions include the selection of points of
	replication and elimination, how many retries can take place, and		replication and elimination, how many retries can take place, and a
	cccccckehblnlcbljtkbcdkrhrjgiibvcidbklbglndf a limit of validity for		limit of validity for the packet beyond which the packet should be
	the packet beyond which the packet should be destroyed rather than		destroyed rather than forwarded uselessly further down the Track.
	forwarded uselessly further down the Track.
	The decision to apply the RAW techniques must be done quickly, and		The decision to apply the RAW techniques must be done quickly, and
	depends on a very recent and precise knowledge of the forwarding		depends on a very recent and precise knowledge of the forwarding
	conditions withing the complex Track. There is a need for an		conditions withing the complex Track. There is a need for an
	observation method to provide the RAW forwarding plane with the		observation method to provide the RAW forwarding plane with the
	specific knowledge of the state of the Track for the type of flow of		specific knowledge of the state of the Track for the type of flow of
	interest (e.g., for a QoS level of interest). To observe the whole		interest (e.g., for a QoS level of interest). To observe the whole
	Track in quasi real time, RAW will consider existing tools such as		Track in quasi real time, RAW will consider existing tools such as
	L2-triggers, DLEP, BFD and inband and out-of-band OAM.		L2-triggers, DLEP, BFD and in-band and out-of-band OAM.
	One possible way of making the RAW forwarding decisions is to make		One possible way of making the RAW forwarding decisions is to make
	them all at the ingress and express them in-band in the packet, which		them all at the ingress and express them in-band in the packet, which
	requires new loose or strict Hop-by-hop signaling. To control the		requires new loose or strict Hop-by-hop signaling. To control the
	RAW forwarding operation along a Track for the individual packets,		RAW forwarding operation along a Track for the individual packets,
	RAW may leverage and extend known techniques such as Segment Routing		RAW may leverage and extend known techniques such as Segment Routing
	(SRv6) or BIER-TE such as done with		(SRv6) or BIER-TE such as done with
	[I-D.thubert-bier-replication-elimination].		[I-D.thubert-bier-replication-elimination].
	An alternate way is to enable each forwarding node to make the RAW		An alternate way is to enable each forwarding node to make the RAW
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